Abort ContextLost.WebGLContextLostFromQuantity if context creation fails.

content/test/data/gpu/webgl.html

Index: content/test/data/gpu/webgl.html
diff --git a/content/test/data/gpu/webgl.html b/content/test/data/gpu/webgl.html
index 2946981947e276d03106f641e3f5880dcaf803b3..7dd2cb334869887ab236896446f08fe399c5ba91 100644
--- a/content/test/data/gpu/webgl.html
+++ b/content/test/data/gpu/webgl.html
@@ -74,6 +74,9 @@ function testQuantityLoss() {
 
     var ctx = c.getContext("experimental-webgl");
     if (!ctx) {
+      console.log("Failed to fetch WebGL context number " + count);
+      window.domAutomationController.send("LOADED");
+      window.domAutomationController.send("FAILED");
       return false;
     }
     ctx.clear(gl.COLOR_BUFFER_BIT);